This proposal is a response to NOT-OD-09-058 Notice of Availability of Recovery Act Funds for Competing Revision Applications. The transmission of genetic material in each cell division requires its accurate duplication and distribution to the daughter cells. The chromosomes are segregated into two equivalent parts by a microtubule-based molecular machine, the mitotic spindle. The parent grant focuses on the assembly and regulation of the mitotic spindle, with emphasis on proteins that bind to the microtubule. These include the gamma-tubulin complex at the centrosome and the Dam1 complex and the Ndc80 complex at the kinetochore. The Dam1 and Ndc80 complexes are required to form strong but dynamic attachments between the chromosomes and the microtubules, but they are not the only components involved. This proposal would fund a new research objective to express and analyze additional kinetochore components to fully reconstitute the microtubule-binding activity of the kinetochore. PUBLIC HEALTH RELEVANCE: Accurate chromosome segregation is required for propagation of all cells. Errors in this process are implicated in oncogenesis, birth defects and cell death. Crucial to proper partitioning of the chromosomes during cell division is the establishment of the mitotic spindle, a microtubule- based molecular machine. The kinetochore is essential for this process.